A police officer runs next to a bus in flames after it was attacked by alleged gang members in Rio de Janeiro
Residents of some of Rio de Janeiro's worst slums are fleeing their homes, hoping to escape a drug war that has left part of the city in ruins.

Smoke rose from the smoldering wreckage of a police helicopter Saturday, while at least eight buses burned and gunfire filled the air in the slum of Morro dos Macacos.

Police say the fighting broke out early Saturday, when one of the city's three main drug gangs invaded the area in an attempt to expand their territory.

At least eight suspected gang members were killed in subsequent gunbattles with police, while two police officers riding in the helicopter were also killed.  Several other people were injured.

Police say the aircraft exploded on a football field after the pilot tried to make an emergency landing.

Hundreds of police officers have been sent into the area to end the fighting.

The outbreak of violence comes just weeks after Rio won the right to host the 2016 Olympic Games.

Rio has long been known for its high crime and murder rates, and has more than 1,000 slums or shantytowns, known as favelas.